It is known for such a breathable gas supply apparatus to include a plurality of gas outlets, e.g. breathing masks, each outlet being fed with gas from a feed line. The apparatus may include a plurality of such feed lines, each feed line feeding a plurality of gas outlets.
Each gas outlet is connected to its respective feed line via a “T” valve which permits the flow of gas in a cabin decompression situation from upstream of the “T” valve simultaneously to the gas outlet and to downstream of the “T” valve e.g. to other downstream “T” valves and gas outlets connected to the feed line.
To protect the gas supply in the event of a breach of the integrity of a feed line, each “T” valve includes a valve member which is moveable into engagement with a valve seat of the valve to close the valve and prevent the flow of gas to downstream of the valve in the event of a breach of the integrity of the feed line downstream of the “T” valve. Such a breach of integrity of a feed line may occur for example in the event of an engine burst when a part of the engine may penetrate the aircraft fuselage and damage or even sever the feed line, thus also causing decompression of the aircraft cabin, or some other calamitous event occurring.
To ensure that the breathing gas supply apparatus is brought to an operational condition as soon as possible after the onset of a cabin decompression, it is desirable to purge the feed line or lines of the apparatus which involves filling the feed line or lines with breathable gas. This may be achieved by providing a purge valve downstream of the gas outlets, which is openable for a short time to permit pressurized breathable gas to flow throughout the apparatus.
However, where conventional “T” valves are provided as described above to protect the apparatus in the event of a breach of integrity of the feed line, the valve members of the “T” valves tend to move to close the “T” valves, hindering the flow of breathable gas throughout the entire apparatus. Furthermore conventionally, the or each feed line includes a non-return valve downstream of the gas outlets connected to the feed line to isolate a damaged or severed feed line. Thus in the event of a breach of integrity of a feed line, the next upstream “T” valve will close to prevent the escape of breathable gas to downstream of the breach, and all gas outlets between the breach and the non-return valve will become unusable.